The present invention relates to an installation for the surface-treatment of components in a liquid bath flowing in a closed circuit.
More particularly, although not exclusively, this may be a (chemical) cleaning or electroplating (galvanoplasty) bath such as is used, for example, for creating a coating by electrolytic deposition of platinum or some other metal, on aircraft engine components.
Known present-day installations generally comprise:                a bath storage reservoir;        a treatment tank to receive the component that is to be treated which is carried by a support tool collaborating with the tank;        respective pipes for conveying the bath from the reservoir to the tank and for emptying the bath from the tank to the reservoir and        motion instigating means for setting the bath in motion in the closed circuit thus formed.        
For example, in the case of treatment installations for actual cleaning proper, said means for setting the bath contained in the closed circuit in motion or for agitating said bath are formed of a recirculation pump which draws in the bath contained in the reservoir to convey it to the tank of parallelepipedal shape via the corresponding pipe that passes through a side wall of this tank, and delivers it from the treatment tank to the reservoir using the other pipe which leads out of the same side wall of the tank. A reciprocating rectilinear motion produced by the component holder tooling itself may be added to these means of setting the bath in motion if the tooling is given the ability to move with respect to the fixed tank, and thus contributes to the agitation of the tank.
In the case of treatment installations which perform electrolytic deposition or the like, the motion instigating means that set the bath contained in the closed circuit in motion once again comprise a recirculation pump. This pump conveys the bath through the relevant pipe from the reservoir to a holed spray boom situated toward the lower part of a side wall of the parallelepipedal tank, near its bottom, and then removes the bath to the reservoir via the other pipe associated with said wall and which extends from a tank overflow element situated in the upper part of this tank.
The component holder tooling may also contribute toward the agitating of the tank through a reciprocating rectilinear motion imparted to it.
With this type of parallelepipedal tank installation with means of setting the bath in motion (or of agitating the bath) using a recirculation pump and movement of the component holder tooling, there a number of disadvantages which arise notably as regards the speed of the treatment bath at the surface of the components that are to be treated.
First of all, because the speed is a resultant of the agitation performed by the recirculation pump and of the moving component hold causing tooling movements to become superposed, it is uneven and disordered (in terms of direction and in terms of intensity) at each point in the treatment tank, which means that it is very different at the center of the parallelepipedal tank compared to the corners thereof.
Moreover, it is difficult to quantify this speed either by physical measurement or by calculation because of the turbulent movement of the bath which is caused by the two sources of motion (the pump and the tooling), because of the angular shape of the tank and because the conveying and removal pipes are positioned on one and the same side wall. In addition, the speed of circulation of the bath cannot be altered to suit the components that are to be treated, the baths used or the desired electrolytic deposition conditions.
It is known in particular that, in galvanoplasty, deposition is dependent on the applied current strength and on the speed of the flow along the tank and therefore along the component that are to be treated. Thus, because it is difficult, for the abovementioned reasons, to control the speed, the bath containing the metallic and other species is not homogeneous at all points in the tank and this means that the quality of the deposit and the thickness thereof are not strictly constant over the entire surface of the components that are to be treated.
Elsewhere, document U.S. Pat. No. 3,551,301, discloses a method for equalizing the electrolytic deposits on a component, from a reservoir of electrolyte of square cross section with parallel anode plates, using conveying and removal pipes which are connected in an aligned fashion to the upstream and downstream ends of the reservoir and a moving support carrying the component that is to be treated. Particularly because the reservoir is of square cross section, the abovementioned problems remain.